year 1958, when he published two systematic papers on Sapotaceae from Borneo with the description of a new genus and two new species. His entomological production lasted longer, from 1954 to 1963. In this period, he published 18 papers, mainly on Ephemeroptera from Southeast Asia and New Guinea, and on Diptera from southern Africa, thereby introducing 14 new species and two new genera. The vast majority of his scientific papers dealt with the systematics and biogeography of the Mollusca. In the early period of his career he published on both marine and non-marine taxa, but the former more or less stopped after 1963, possibly related to his move from a marine institute at Port Elizabeth to the Natal Museum at Pietermaritzburg. Most of Dolf's scientific work has been devoted to land snails, especially those from subsaharan Africa and the islands surrounding this continent. Although there are few families on which he has not published, there are three families that may be considered his particular area of expertise and fascination: the pulmonate families Streptaxidae and Achatinidae and the operculate (caenogastropod) family Maizaniidae. The interest in the carnivorous family Streptaxidae was undoubtedly raised by Dolf's prolonged stay in South Africa, quite possibly inspired by Matthew William Kemble Connolly’s (1939) impressive monograph on the South African non-marine Mollusca, in which a picture of an extremely diverse and aesthetically appealing streptaxid radiation was painted. In all, he described three new genera and 60 new species and subspecies of Streptaxidae, all but four from Africa. Achatinidae are a family of rather large land snails, and, in spite of their size, one that poses tremendous taxonomic problems, and Dolf is one of the few people who knows his way in the chaotic taxonomy of this group. He devoted various papers partly or wholly to the family and introduced six new species and subspecies. He was a friend of the recently deceased American Achatinidae specialist Albert Raymond Mead (1915–2009). They regularly exchanged opinions, but did not publish jointly. A third group that apparently has his special interest are the terrestrial operculates, formerly known as ‘Prosobranchia’, a heterogeneous assemblage of gastropods with an operculum and separate males and females (in contrast to the hermaphrodite pulmonate land snails). Operculate gastropods appear to be particularly poorly represented in subsaharan Africa in comparison to other continents, especially tropical Asia. Since the early 1980s Dolf has taken it on him to revise